1. Field of the Invention
This invention relates to a display device of the reflection type for a vehicle wherein a display image on a display unit is reflected toward a driver's seat of the vehicle by a reflecting face of a reflecting element provided on an instrument panel of the vehicle to provide driving information to a driver.
2. Description of the Prior Art
Display devices for a vehicle are conventionally known wherein a reflecting face of a reflecting element is utilized to effect remote indication in order to assure high speed visual observation of a displayed image. An exemplary one of such display devices is shown in FIG. 14.
Referring to FIG. 14, the conventional display device shown includes a display unit 23 such as a liquid crystal display unit or a fluorescent character display tube mounted on a lower face of a meter hood 22 of an instrument panel 21 of a vehicle. A half mirror 24 is disposed on a meter display section of the instrument panel 21. A display image of the display unit 23 is projected onto the half mirror 24 so that a virtual image 25 of the display image of the display unit 23 may be visually observed by way of the half mirror 24.
The virtual image 25 visually observed in this manner is formed at an interior position spaced by a distance equal to the distance between the half mirror 24 and the display unit 23 rearwardly of the half mirror 24, thereby obtaining an effect of remote indication.
However, the effect of remote indication cannot be obtained sufficiently with such a display device a the device shown in FIG. 14 wherein light is reflected only once by a half mirror.
Referring now to FIG. 15, there is shown another exemplary one of such conventional display devices as described above. The display device shown includes a reflecting plate 36 disposed in an opposing relationship to a half mirror 34 in a meter hood 32 of an instrument panel 31 of a vehicle. A display device 33 is disposed in an opposing relationship to the reflecting plate 36 in the meter hood 32. A display image of the display unit 33 is projected to the half mirror 34 by way of the reflecting plate 36 so that a virtual image 35 displayed on the display unit 33 may be visually observed by way of the half mirror 34 and the reflecting plate 36.
With the display device of FIG. 15, a path of light of a long distance is assured from the display unit 33 to the mirror 34, and a higher effect of remote indication than that, for example, of the device of FIG. 14 can be achieved.
However, where light is reflected by two or more times in order to assure a long path of light as in the display device of FIG. 15, a comparatively great volume is required for such path of light, which requires a comparatively great overall size of the display device.
It is to be noted that reference numeral 27 in FIG. 14 and reference numeral 37 in FIG. 15 denote each another display unit which can be visually observed in an overlapping relationship with the virtual image 25 or 35 displayed by the display device.
By the way, with a display device which makes use of a reflecting face of a reflecting element so that a virtual image displayed on a display unit may be visually observed as described above, due to a relationship of an amount of light reflected from the reflecting face, only a display pattern of the display unit from which light is emitted can be visually observed such that, for example, a light emitting segment itself of a fluorescent character display tube can be visually observed while any other portion of the fluorescent character display tube than the light emitting segment cannot be visually observed. Accordingly, in a display device of the type described, there is an advantage, in addition to an effect of remote indication, that a large amount of light can be obtained with the display unit and accordingly a high contrast in display can be assured. Further, a display image can be seen clearly on the dark background, and generally the quality of a display image is higher than that of a display unit of the direct vision type.
It is to be noted that such advantages described just above are derived from the fact that a display pattern emits light, and in order to allow a displayed image to be visually observed for practical use, a self light emitting display unit is employed in such a display device of the reflection type as described above.
Generally, a digital display unit is employed popularly as a display unit of the self light emitting type, and also such a display device of the reflection type as described above normally employs a digital display unit. However, a digital display unit is normally expensive comparing with an analog meter, and consequently, a high cost is required for a display device in which a digital display unit is employed. Further, drivers of automobiles are progressively inclined to have a taste of an analog meter, and development of a display device of the reflection type which employs an analog meter is demanded.
It is to be noted that analog meters of the light emitting type which are directed to display at night are also known, and an exemplary one of such analog meters of the light emitting type is shown in FIG. 13. Referring to FIG. 13, the analog meter shown includes a meter mechanism 41, a dial 42, and a light introducing plate 43 interposed between the meter mechanism 41 and the dial 42. Thus, light from a pair of light source bulbs 44 is introduced into the light introducing plate 43 by way of the opposite ends 43a so as to cause the light introducing plate 43 to emit light behind the dial 42 so that light transmitting graduations and so forth formed on the dial 42 may look such that they emit light therefrom.
However, since a sufficient amount of light cannot be obtained with an analog meter wherein light is directly irradiated upon a back face of a dial using a light introducing plate in this manner, it cannot be employed in a display device of the reflection type.